In Public Switched Telephone Networks (PSTNs) additional end user services are commonly provided in addition to the facility to make ordinary telephone calls. For example, prepaid calling, call forwarding, call redirection or ring-back services. Such services are commonly implemented using Intelligent Network (IN) technology that uses Service Switching Points (SSPs) to trigger Service Control Points (SCPs) to provide these additional services in the PSTN. Such IN services may be implemented in an IN Service Creation Environment (SCE) that enables service designers to build the appropriate service logic into corresponding SSPs and SCPs.
Internet Protocol (IP) networks are increasingly used to provide the functions of PSTNs, using Voice over IP (VOIP) technology. IP networks may be interconnected with PSTNs to provide such PSTN functions to VOIP subscribers. VOIP is implemented using protocols such as Session Initiation Protocol (SIP), Session Description Protocol (SDP), Real-time Transport Protocol (RTP), and Real-time Transport Control Protocol (RTCP). However, providing PSTN services on VOIP networks is costly as it normally requires new SCE development. Furthermore, engineers need to be re-trained in using these new SCEs.